Which plant protein has the best amino-acid profile?

Soy protein isolate is the only widely commercial plant protein with a DIAAS approaching whey territory (~0.90), driven by a complete essential-amino-acid profile and high digestibility. Pea protein follows at DIAAS roughly 0.65–0.75 in isolate form, with the sulphur amino acids (methionine and cysteine) as the rate-limiting amino acids. Rice protein alone sits at 0.40–0.55 (lysine-limited), but in a 70:30 pea-rice blend the DIAAS rises to 0.80–0.85 because pea and rice have inverse limiting amino acids. Hemp and pumpkin sit lower (~0.45–0.55) on DIAAS and have notably lower protein density per gram of powder.

Should I worry about soy isoflavones?

The published meta-analyses on circulating sex hormones in adult men (Hamilton-Reeves JM et al. 2010; Reed KE et al. 2020) found no significant effect of soy protein or isoflavone exposure on testosterone, free testosterone, or estradiol at typical dietary or supplement doses. Cohort data in East Asian populations associates higher soy intake with lower breast cancer incidence; Western cohort data is less clear but does not show increased risk. Soy can interfere with levothyroxine absorption when taken close together — this is a documented drug interaction in the BNF, not a population-wide thyroid effect. Whether to include soy in the diet on these grounds is an individual decision.

Why is rice protein so cheap?

Rice protein concentrate is a high-yield byproduct of rice-starch extraction. Brown rice is abundant, the enzymatic-extraction process is mature, and the resulting concentrate has lower amino-acid completeness than pea or soy, making it less commercially valuable on its own. The cheap bulk powder is then either sold direct (more often in food-ingredient channels than retail) or, more commonly, blended with pea to produce a complete-amino-acid blend. The retail price you see on a pea-rice blend reflects the blended cost plus brand markup, not the rice-protein-isolate cost alone.

Cheapest plant-based protein UK?

On April 2026 brand-direct UK pricing, MyVegan's Pea Protein Isolate at approximately £21.99/kg works out to roughly £0.80 per 30 g of protein, narrowly ahead of MyVegan's Soy Protein Isolate at roughly £0.85 and Bulk's Pea Protein Isolate at roughly £0.86. The single-source pea and soy isolates from supplement-channel brands consistently sit at the cheapest end of the plant-protein category and are competitive with whey concentrate on per-30g-protein cost. Promotional cycles can shift these prices 10–20% in either direction.

Are blended plant proteins better than single-source?

On amino-acid completeness, a well-designed pea-rice blend at roughly 70:30 by protein mass has a higher DIAAS (~0.80–0.85) than pea alone (~0.65–0.75) or rice alone (~0.40–0.55) because the two sources have inverse limiting amino acids. On cost per 30 g of protein, retail blends typically command a 30–80% premium over single-source pea or soy isolate from the same channel. Whether the amino-acid completeness premium is worth the cost premium depends on whether the user gets the rest of their amino acids from a varied diet (in which case single-source pea is sufficient) or relies on the powder as a primary protein source.

Does grass-fed whey beat any plant protein for muscle?

On controlled head-to-head trials, whey protein (concentrate or isolate, typically not specified as grass-fed) produces marginally faster acute muscle protein synthesis stimulation than equivalent doses of pea or soy, attributed largely to whey's higher leucine content (11–12% vs plant proteins' 7–9%). Over multi-week resistance-training trials at equivalent total-protein doses (Banaszek A et al. 2019 for pea vs whey; Joy JM et al. 2013 for rice vs whey at higher doses), differences in lean mass and strength gains are typically not statistically significant. Grass-fed status specifically has no consistent trial evidence supporting superiority over conventionally-fed whey on muscle outcomes. Whether whey 'beats' plant protein for muscle is highly dependent on dose, training stimulus, and trial duration; the marginal advantage is real but smaller than marketing suggests.

Plant-Based Protein UK: Pea, Soy, Hemp, Rice — Comparison (2026)

Nutripedia Research Team21 April 2026

Updated 30 April 2026

Plant-based proteins differ at the amino-acid level in ways that matter for cross-product comparison. We walk through pea, soy, rice, hemp, and pumpkin profiles, present the soy isoflavone evidence neutrally, and compare UK plant protein brands on per-serving cost — without recommending anyone take a supplement.

Not medical advice

Nutripedia summarises published peer-reviewed research. This content is for informational purposes only and is not a substitute for professional medical advice. Product mentions are not endorsements.

Before You Read This

Nutripedia is a research librarian, not a doctor. Nothing on this page is medical advice. This article describes the chemistry and per-serving cost of plant-based protein products on the UK market in 2026 — it does not recommend that any reader consume any of these products and does not interpret symptoms. Consult a UK GP, NHS pharmacist, or registered dietitian before starting any supplement, especially if you are pregnant, breastfeeding, on medication, or managing a chronic condition. Plant proteins may contain allergens (soy, peas as legumes, gluten in some rice protein blends) and are sometimes contraindicated in specific clinical contexts; those decisions are clinical, not commercial. Brand prices reflect retail listings as observed in April 2026.

Our research is based on 75 peer-reviewed studies. View the full evidence database

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Nutripedia is an educational resource. Content is sourced from peer-reviewed studies and does not constitute medical advice. Product mentions are not endorsements. Consult a healthcare professional before starting any supplement.

Reviewed by

Archie Roberts

Founder, Nutripedia — ALDR Ltd

This page summarises published research from PubMed, NHS, EFSA, and SACN. It does not constitute medical advice; consult a qualified healthcare professional before changing any supplement regimen.

Last reviewed: 30 Apr 2026Methodology